Effect of reclaimed municipal wastewater on ryegrass growthand soil phosphorus conversion

Ryegrass was irrigated with reclaimed municipal wastewater (RW), 1∶1 clean water and reclaimed municipal wastewater (CW+RW) and clean water (CW) as the control in the pot experiment in a greenhouse to study the effects of reclaimed municipal wastewater on ryegrass growth, conversion characteristics of soil phosphorus and the implications for agricultural production in China. The findings suggested that in comparison with the control, reclaimed municipal wastewater significantly increased aboveground and root biomass of ryegrass. While CW+RW increased aboveground and root biomass by 18.92% and 6.42%, RW increased these parameters by 26.79% and 10.55%, respectively. CW+RW and RW increased P concentration in aboveground ryegrass by 8.48% and 10.93%, respectively. Reclaimed municipal wastewater irrigation apparently reduced total soil P concentration. Olsen-P concentration was significantly increased, respectively, by 29.15% and 43.80% under CW+RW and RW treatments. CW+RW and RW also increased active organic phosphorus concentration by 50.30% and 81.57%, respectively. They, however, increased moderately active inorganic phosphorus by 7.66% and 13.68%, respectively. Ca₂-P concentration was enhanced under CW+RW and RW treatments, increasing from 12.90 mg·kg^-1 of the control to 16.42 mg·kg^-1 and 15.49 mg·kg^-1 with increment of 27.29% and 19.38%, respectively. CW+RW and RW also increased Ca8-P concentration by 19.94% and 16.03%, respectively. Reclaimed municipal wastewater irrigation increased soil P activity by decreasing soil pH and significantly increasing soil organic matter content. Reclaimed municipal wastewater irrigation was definitely improved soil phosphorus utilization efficiency.